It is known that the transmission of facsimile signals, over a telephone line, towards a receiver necessitates the use of a buffer-memory loaded by the facsimile signals coded in digital form when the out-put rate of the transmitter or receiver terminal is greater than the permissible flow-rate for the transmission line. The buffer-memory is unloaded so as to allow the transmission of coded facsimile signals over the line under optimum conditions for the transmission lines. The role of the buffer-memory is thus essentially to match the transmission speed of the line to the scanning speed of the document by the transmitter equipment, or the transmission speed of the line to the reproduction speed of the document by the receiver equipment.
In known transmitter equipment, with the scanning speed of a document greater than the speed of transmission over the line, a load-unload control member of the buffer-memory transmits a signal which interrupts the analysis of the document until the memory is sufficiently unloaded to allow the analysis of the document to be continued. This equipment operates by the scanning of successive lines of the document. A synchronisation term is coded and transmitted with the facsimile signals to distinguish the successive scanning lines of the document, this synchronisation term differing from the coded facsimile signals so that it is not confused with them and can be easily separated from them in the receiving equipment.
In the known equipment, these buffer-memories are generally constituted by MOS memories (shift registers). The signals given by the analysis of successive lines of a document are received by these memories which easily allow the speed of analysis to be matched to the speed of transmission along the line, or the speed of reproduction to the speed of transmission along the line, at the receiving end. However the resulting memory circuits are very burdensome and voluminous.
In other known equipment, the buffer-memory which matches the speed of scanning of a document, or the speed of reproduction of a document, to the speed of transmission of data between the emitter and receiver, can be constituted by a magnetic tape recorder. The totality of the data to be transmitted, or which has been transmitted, can be recorded on the magnetic tape. The drive of the magnetic tape at a variable speed during recording and play-back, allows the speed of transmission of the data to be matched to the bandwidth of the channel used, thus rendering independent the speeds of analysis or reproduction of a document from the speed of transmission over a distance of the information.
It is also known, in such equipment making use of an intermediate recording of data on magnetic tape, to associate two auxiliary memories with each magnetic tape which at the transmission end are arranged up-stream of the magnetic tape, and at the receiving end down-stream of the magnetic tape. The pair of memories associated with magnetic tape are alternatively loaded and unloaded, the magnetic tape having an intermittent stop-start drive. For example at the transmission end one of the memories is loaded by the data coming from the analysis at the frequency of the analysis; when it is full the information from the analysis loads the second memory while the contents of the first memory are transferred to the magnetic tape thus driven. When the first memory is empty, the tape stops. The tape is again driven for the transfer of the contents of the second memory when this is full, then stops when it is empty, and during this last transfer the first memory is again loaded and the transfer process continues until the complete recording of the data on the magnetic tape.
Where a signal is recorded in binary code, on magnetic tape, it is also known to associate a synchronisation signal with this signal which can be recorded on auxiliary track.